In the dispensing field, it is common to mix two or more fluid components to form a mixed fluid shortly before dispensing. For example, first and second fluids, such as first and second liquid adhesive components may be mixed to form a curable liquid adhesive for application onto a workpiece or substrate. The first and second liquid components are each separately contained within a dual-chamber cartridge. A nozzle is attached to component outlets of the cartridge and pressure is applied to the first and second liquid components in order to force the first and second liquid components into the nozzle. A static mixer is also positioned within the nozzle. Accordingly, the first and second liquid components travel through the static mixer within the nozzle to dispense from a nozzle tip for application onto the workpiece or substrate. While this particular example forms a curable liquid adhesive for dispensing, any number of fluid components may be similarly mixed to create a mixed fluid that includes any variety of desirable properties for use by the end-user.
In many cases, the two or more fluid components are directed into the mixing nozzle in unequal volumes at a predetermined ratio. Thus, upon initially dispensing the fluid components from the cartridge, a lead-lag condition may occur in which the smaller volume fluid component of the predetermined ratio “lags” behind the higher volume fluid component. This lead-lag condition results in the initially dispensed fluid having an incorrect ratio of fluid components. Any mixed fluid dispensed during the initial lead-lag condition must be discarded.
Often, the cartridge outlets are in a side-by-side configuration. The side-by-side configuration produces a cross-section of fluid also having the fluid components in side-by-side contact. Thus, the fluid components remain relatively unmixed, which may greatly reduce beneficial properties of the mixed fluid. For instance, improperly mixed liquid adhesive may not effectively cure, causing partial or total failure of the adhesive in use.
In order to improve fluid component ratio accuracy and mixing of the fluid components, the static mixer may include a pre-mixer adapted to both reduce lead-lag and layer the fluid components into a pre-mixed fluid. The pre-mixed fluid then passes into the static mixer partially mixed and having more accurate fluid component ratios. However, pre-mixers often include complex geometries defining fluid paths for the fluid components that are difficult to form. Moreover, these complex geometries create significant restriction between the cartridge and the nozzle causing flow problems, especially with high viscosity fluid components.
There is a need for a dispensing assembly and method for use in dispensing a mixed fluid, such as a mixed adhesive liquid, that addresses present challenges and characteristics such as those discussed above.